The transplantation of autonomic ganglia has been extended to CNS tissue. Hypothalamic tissue from 17-day-old rat fetuses has been transplanted to the intact surface over the area postrema of 6 day old rats. Three months later, the hypothalamic graft contains many neurons and a rich neuropil including what appear to be neurosecretory axons. Survival of these large transplants is due to establishment of anastomses with meningeal blood vessels. During degeneration of hypoglossal (XIIn) axons after nerve crush, the neuron-specific enolase (NSE) of the XIIn neurons begins to fall during the first 10 days and returns to normal levels between 30 and 45 days. There does not appear to be a rise in non-neuronal enolase (NNE) during the fall in NSE; there is no switch from one type of enolase to the other as we have found during development. This first demonstration of a change in the amount of glycolytic enzyme during degeneration and regeneration has also revealed small neurons that are unaffected by nerve crush. They appear to be interneurons.